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Questions tagged [iterator]

An iterator is an object-oriented programming pattern which for the most part functions similarly to a pointer to an object inside a collection with the added ability to traverse through the collection in a defined manner, agnostic of the actual implementation or even object addresses in physical ...

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51 views

Handling related generic type parameters

In answering a question on StackOverflow, it occurred to me that a more generic version of GroupBy for C# that delegated membership in each group to a class could ...
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Grouping consecutive values together in python [on hold]

from itertools import groupby, count groupby(numberlist, lambda n, c=count(): n-next(c)) Above code works perfectly and is taken from previous post. I was not ...
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1answer
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putting sql-query response directly to foreach-loop?

Is there any reason to not do this? Putting the query directly inside a foreach-statment when the only time the result is going to be used is within that location.. ...
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4answers
756 views

Basic iterator supporting vector implementation

On the fly, I just implemented this iterator supporting vector class to understand how range-based for loop works. It's really basic but let me know what can be improved. Vector.h ...
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3answers
123 views

Endless stream: stream a range and return default value if the range is exhausted

Introduction: Motivation Sometimes there is a need to merge N > 1 ranges, and they don't have equal length, but there is a value which can be used in case the range is already exhausted. It is ...
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3answers
999 views
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2answers
183 views

Iterator for BFS binary tree traversal

I implemented an iterator pattern for C# using IEnumerator and IEnumerable. The goal of the implementation is to traverse a ...
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0answers
37 views

Identifying objects as some type of enum

Please review my code. It works as it should but I think about making it more pretty or optimal. This method should take in some IEnumerable of ...
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2answers
60 views

Iterable object on set of ids

For some of the algorithms that I am implementing it turned out to be useful storing ids in order to iterate on objects, while also avoiding having to think about reallocation and invalidation of ...
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4answers
88 views

Implementing a custom iterator by inheriting from an existing iterator class and overriding operator*

My goal is to write very little code and I want a custom iterator that only changes the behavior of the dereference operator* but copies the rest of the behavior ...
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0answers
37 views

General use multi-dimensional container using operator[]

This is a followup to a previous question of mine on same subject. Context I want to have a tool that allows to simulate as much as possible a C++ standard container for a multidimensional ...
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1answer
182 views

Getting serial port list

Needed to get a local serial port list. System.IO.Ports.SerialPort.GetPortNames() returns names but not the descriptions like you can see in Device Manager: ...
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1answer
72 views

Flatten nested iterables

I wrote a program sometime ago that reads csv files, sorts, reorders and groups their columns/rows' content (with itertools) and later labels the groups using a ...
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2answers
163 views

Multi-dimensional container using operator[]

This is a late followup to a previous question of mine on same subject. Context: I want to have a tool that allows to use all the C++ goodies (algorithms, for loop on containers, etc.) on a ...
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1answer
50 views

Implementation of generic unordered list in java

This question is a follow-up question of this question. These features are added to the new class - Generic class User is capable of setting the size ...
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2answers
91 views

Generic in order traversal iterator for binary trees

This actually started off as member type for the binary_search_tree, but after realizing that it doesn't compare to values or use the value objects inside of it, I ...
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2answers
56 views

Acts like an iterator, but counts

I’m making a “counting iterator” which emulates a constant container of consecutive values of some integral type. It is mostly boilerplate, going through the list of requirements for different ...
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1answer
68 views

Custom container for iterating over combinations of elements from multiple sets

Motivated by some SO quesitons [1, 2] I made an attempt at implementing a custom container with a bi-directional custom iterator for iterating over all combinations of elements from multiple sets. I ...
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2answers
693 views

Determine added, removed and kept items between two lists

My code is determining the difference between two iterables in terms of items that have been addded, removed and kept. The items are assumed to be sortable and there are no duplicates. ...
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1answer
90 views

Poor decision of IEnumerable of IEnumerable of IEnumerable [closed]

I wish to improve a class design that causes me readability and performance problems as the code grows. ...
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8answers
2k views

Counting elements meeting a predicate in an enumerable without iterating the entire sequence

I was reading this question, and the answer that mentioned streams, and a thought had occurred to me. In many cases (at least in my usage) I want to determine if a sequence (or ...
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1answer
68 views

Iterator over a container with indexing operation

This is a random access iterator that stores an index and a reference to a container. It iterates over any container with indexing operation. It does not have copy assignment / move assignment ...
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2answers
284 views

Parsing oscilloscope binary data file with C++

Preliminaries I have OWON oscilloscope that is able to record waveform in file in three formats: Text format .txt: the first lines are some general information ...
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0answers
62 views

Iterator for custom List class

I have extended a custom list class I have been working on with a Iterator class. I have not used std::iterator as a base class as it will be deprecated in C++17. ...
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2answers
527 views

Custom C++ random access iterator for pointers to arrays

I have implemented a custom iterator to iterate over an array that is held by a pointer. The iterator accepts a unit which specifies by which amount the underlying pointer is increased (or decreased) ...
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0answers
182 views

Helper trait for modularizing iterator chains which involve grouping items in tuples

The itertools::Itertools::tuples method from the itertools crate appears to be limited in the aspect that the trait ...
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1answer
84 views

Lazy lists with transformations, using generators & iterators

I built this very-basic lazy list (I'll add more methods as I need them). You provide it an array, a generator or any iterator. It creates a lazy list, which lets you run a pipeline of transformations ...
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3answers
521 views

Compute Convex Hull

The question asks to compute the convex hull of a set of 2D points. A convex hull is basically a series of consecutive line segments that suffice to enclose all the points in the area. In this ...
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1answer
660 views

Check if multiple lists contain an element from a large external list

I have a list of lists (many tokenised sentences). For anyone who doesn't know what tokenised sentences are, my list is like so: ...
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2answers
258 views

Example of adding STL iterator support to custom collection class

I'm trying to create an example of a custom collection with an API meeting the requirements of STL iterator templates, as a learning experience. The collection used here, a ring buffer, is merely a ...
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0answers
33 views

Using Generators for private scope

There's something about this code that's pretty neat-o to me, but is it a bad idea? Is there a name for programming like this? First, the generator itself: ...
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1answer
102 views

C++ container — variable byte coded numbers list

I'm writing a container for unsigned integers, which uses variable byte coding. It works but some decisions I took look ugly so I would be glad if you gave me some hints for improving the design. I ...
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3answers
203 views

Merge sorted lists, removing duplicates

I want to merge two sorted lists of Integers but this is not the general mergesort case because the same number may appear in both lists. (However, each number can only appear once in a particular ...
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0answers
117 views

Implementing a tabular pretty-print using Java 8 Stream API

About six years ago I implemented a simple tabular pretty-print Java class that mostly simulated MySQL CLI query result tables. I don't really like it because it was implemented in a, I believe, ...
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1answer
79 views

Retrieving synonyms from an ontology

My question is about my Ontology which retrieves synonyms from the ontology by using isSynonymOf object property. (Note that my Ontology file is 260 kb and expected to become 500kb). I am ...
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2answers
249 views

Lazy split and semi-lazy split

Sometimes I need to be able to split data into chunks, and so something like str.split would be helpful. This comes with two downsides: Input has to be strings You ...
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0answers
36 views

Apply arbitrary action during recursive generator function

I've got this recursive generator function. It will traverse an object looking for "leafs", any keys that don't point to sub-objects. Then it applies one of two actions on the leaf and yields it. Any ...
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1answer
560 views

Merge n sorted iterators

Over the weekend I was curious about efficiently merging multiple sorted iterators together, and for them to be in sorted order. This is quite like a challenge on HackerRank: You’re given the ...
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2answers
134 views

Iterator of Container of Container

Based on this question I though I would pull together an iterator that iterated over a container of containers. ...
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3answers
1k views

Table of Tribonacci sequence using NumPy and PANDAS

What I am trying to accomplish is calculate the Tribonacci numbers and the ratio. I can do this in Excel easy like this. So I tried do the same using Python 3 now. It works and gives such output. ...
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2answers
205 views

A C++ custom iterator for indirection iteration

This program does not quite conform to the previous related question, yet does basically the same thing: given a collection of elements and a collection of indices, return via an iterator collection ...
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1answer
63 views

File names to database table

I have files in subfolders on a network drive. I want to create a list of files, and insert that list into an Oracle table. I can successfully iterate through the files in the subfolders and do the ...
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2answers
630 views

Interleave two lists of strings

I've got a fairly simple task here, but I think it's worth trying to perfect the implementation, because I can probably learn a thing or two about using .NET's enumerables correctly in the process. I ...
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1answer
124 views

First all zero row of a matrix in C++

The problem of finding the first all zero row in a NxN matrix was featured in a letter to the CACM in 1974 by Frank Rubin who claimed it was a problem for which using a ...
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1answer
66 views

Loop + Take for repeatedly taking elements from the same collection

I sometimes need to enumerate the same collection multiple times so I wrote an extension that does this for me. I call it Loop. It takes one optional parameter <...
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0answers
78 views

Lag Lead Enumerator

I had a need to do a look-ahead and look-behind when enumerating though and IEnumerable. Here is a classic situation: ...
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1answer
469 views

Binary search tree in C++ 17 using iterator pattern

I am new to C++ and am attempting to write the following binary search tree using the iterator pattern (and std::optional in C++17): ...
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2answers
229 views

Lazy string_view splitter range

Trying something out of my comfort zone here, and attempting to implement a D-style range around std::string_view. Looking for any and all suggestions or ...
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0answers
37 views

Iterator structure for block and interlace counting schemes

We have a set of time slices, in the order of 50. Throughout this question I will use 6. We group these slices into blocks, in this example the block size is 2. Then we want to iterate through all ...
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3answers
400 views

Find median of two sorted ranges

Given two sorted ranges of elements, compute a median of all the elements in O(log(n+m)) time. This solution contains only one call to std::lower_bound ...